Airservices
Australias Flying Unit ceased operation on 6 February 1998 after 60 years
of service to the aviation industry and the flight inspection function was contracted
out to be performed on behalf of Airservices by Pearl Aviation.

This brief history concentrates on the flight testing of navigation aids rather
than the fleet of about thirty types of aircraft which the Department has owned
for this and other purposes, or the training of pilots, inspection of aerodromes
and air routes, search and rescue, post-accident investigations or the carriage
of VIPs. It is of historical interest, however, to note that one of the Department's
first aircraft, a DH-50 (registered G-AUAB) made
the first round Australia landplane
flight in 1924.

Flight
calibration of navigation aids essentially comprises three elements: a specially
equipped aircraft to fly along the radio course in space radiated by the beacon
(e.g. the instrument landing system); a ground measuring device which can accurately
plot the aircrafts flight path; and a precision laboratory where the equipment
can be accurately calibrated.

The
flight calibration of radio and electrical navigation aids has been a function
of the Department and its predecessors since 1937. The first radio navigation
aid was the 33MHz Lorenz Radio Range,
ten of which were installed in 1936-1938 but could not be used operationally until
they had been flight-tested. The Civil Aviation Board (CAB)
wanted to buy a Lockheed for this purpose, but was compelled by the government
to "buy British". In the meantime, a direct result of the inquiry into
the crash of the Douglas DC-2 Kyeema which struck Mount Dandenong on 25
October 1938 was a Government instruction for the Civil Aviation Board to calibrate
the Lorenz radio ranges and a Guinea Airways Lockheed 10A (VH-AAU)
was hired to flight test the beacons.

The
CAB later purchased its own aircraft, Percival Q.6 VH-ABY
for the purpose, but it proved unsuitable.

In
1946, the Department of Civil Aviation (DCA)
acquired two war-surplus Douglas C47 transport aircraft, registered
VH-DMV and VH-ASD (later re-registered as VH-CAO and VH-CAN) for the purpose
of flight testing radio navigation aids. On delivery from Manila they were fitted
out with special radio equipment by Butler Air Transport in Sydney so that they
could flight test the Visual Aural Range (VAR)
which superseded the Lorenz beacon, Localizers (the Glide Path came later), Non-Directional
Beacons (NDBs, then called Homers)
and, later, Distance Measuring Equipment (DME).

A
kitchen was fitted in the rear of the aircraft so crews could be self-sufficient
on long flights, but the facility was rarely used and was later removed. The ground
tracking equipment was a Watts pilot balloon theodolite and wartime SCR522 VHF
transceiver. Two more C47s were acquired later.

In
1955 the Flight Test Section was formed as a Division of the Airways Planning
and Investigations Branch. It was initially under the control of Stan Joyner and
Max Cassidy. Max Crisp was in charge of the Flight Inspectors (technicians), who
were located in the DCA laboratory near the Maribrynong Munitions Works, with
the DCA pilots based in DCA headquarters at Henty House and the aircraft located
at Essendon Airport.

The
introduction of Viscounts,
Convairs, etc in the mid-1950 necessitated Flight Test aircraft capable of flying
at the height, speed and tracks of these new aircraft types. Two Fokker F.27 aircraft,
VH-CAT and VH-CAV
were purchased, and arrived in November 1959. A third F27, VH-TFE
was later acquired and used primarily for training, calibration of visual aids
and VIP transport.

Sites had to be selected for beacons, and the whole airways system had to
be regularly inspected to ensure that it met the stringent requirements of ICAO
Annexe 10.

In 1959,
the Director General of Civil Aviation, Mr D.G.
Anderson, CBE, directed Captain Frank Shannahan to establish the DCA
Flying Unit, entirely based in Hangar
3 at Essendon Airport, and forming part of the Head Office Operations
Branch. Frank was appointed Superintendent, and under him were five sections:
Pilots; Flight Surveyors/Laboratory Technicians; Engineers/Draftsmen;
Aircraft Maintenance; and Administration Support.

With
the introduction of jet aircraft on domestic air routes in the mid-1960s, a Hawker
Siddeley HS125 (VH-CAO) was added to the Flying
Unit fleet in 1964, and the F27s were later replaced by three Fokker F28 Fellowship
aircraft in 1976/77 (VH-ATD, VH-ATE
& VH-ATG).

All
the passenger seats with the exception of the last three rows were removed from
the F28s to provide space for two large flight survey consoles and racks of equipment.

Two
aircraft surveyors, John Ayres and Rod Torrington worked in Holland between the
end of 1974 and April 1977 while the aircraft were modified and fitted out with
the technical equipment, including 37 antennae. By now the navigation aids tested
included full ILS, VOR, radar
and T-Visual Approach Slope Indicator System (T-VASIS).

The
function of tracking the aircraft from the ground was for many years performed
by two technicans - one operating a theodolite to track the aircraft, and the
other relaying these bearings back to the aircraft via a portable VHF transmitter.
There were drawbacks to this labour-intensive method, namely the requirement for
good visibility and a high ceiling, and the costly delay while the technicians
with the theodolite drove to a remote site.

One
of the Units notable technical achievements was the development of an optical
tracking system which automatically tracked the flight path of the aircraft and
transmitted the bearings back to the aircraft.

There was nothing
suitable on the market, so DCA invented its own. The system was simple but very
effective, and DCA decided to patent it. Imagine their surprise to find that they
had reinvented, and improved on, the USA Trident nuclear missile guidance system!
Notable contributions made in this area were made by Brian OKeeffe, Frank
Partridge and Keith Farmer. Several versions were produced, and Peter McNab recalls
a DC3 being tracked from a distance of 32 miles.

The
Flying Unit was acknowledged to be a world class facility. Overseas visitors recognised
the quality and value of the service it provided. This was attributable to a number
of factors: the suitability and the fitting out of its flight calibration aircraft;
the professionalism of its staff; and the quality of its research and development.
It was this latter which contributed to the development of Distance Measuring
Equipment in the 1950s, the T-Visual Approach Slope Indicator System (T-VASIS),
the Microwave Landing System (Interscan),
and (more recently) GPS.

At
its zenith the Flying Unit had a staff of over 100, maintained 25 aircraft, and
was responsible for 640 navigational aids. Fron the early 1960s, the Units
expertise extended beyond Australia and New Guinea to Fiji, Norfolk Island and
Indonesia. In the 1990s it also serviced the Australian Defence Forces navigation
aids and the airways systems in New Zealand, Vietnam,
and the Philippines. Their patch covered one ninth of the earths surface
area, which was a remarkable achievement.